Proposals have been made as to various types of molding methods wherein filling materials consisting of heat resisting particulate materials are maintained by negative pressure, thereby forming cavities.
In conventional methods, a mold is formed by binding or hardening the whole mold, using a sand which includes a binder. As the filling material experience has shown that there has been a falling-down or slacking-down of the filling material of the mold into the cavity, in case of insufficiency of the binder, or shock by handling. Sometimes the shaping surface of the mold is washed away by the running of the molten metal.